Cloning

[Mjolnir]

Is this valid code for a shallow clone?

x=(MyClass) y.clone();

[abc123]

no

[abc123]

maybe.

[Belisarius]

It's valid only if MyClass implements clone(), as it's not implemented by Object, only defined.

Personally, I think calling a method on the same line as class casting is a bit ambiguous. You probably ought to make y an instance of MyClass as soon as y is defined. For instance, if you get it out of an ArrayList:

MyClass y = (MyClass)list.get(i);
MyClass x = y.clone();

I don't know if that's possible in your situation, but you might want to give it a shot.

I've never heard of the term "shallow clone" before. What is it?

[npa]

Originally posted by Belisarius
It's valid only if MyClass implements clone(), as it's not implemented by Object, only defined.

What makes you think that?

Read this: http://forum.java.sun.com/thread.jsp...rt=0&trange=15

And then: http://developer.java.sun.com/develo...a/Chapter3.pdf

[Belisarius]

The Java API. See clone() in Object:

The class Object does not itself implement the interface Cloneable, so calling the clone method on an object whose class is Object will result in throwing an exception at run time.

[Belisarius]

Anyways, Josh Block in Effective Java spends a lot of time says that unless you have a very specific need for clone, don't use it. Chances are if you're asking about how to use clone in such a simple context, you shouldn't be using it.

[npa]

Originally posted by Belisarius
implements clone(), as it's not implemented by Object,

That was a little confusing, I thought you meant it
did not implement the "clone()" method, which it does.

That was my point.

[Belisarius]

I might be mangling my jargon. I meant that it doesn't implement clone() as one implements methods in a class that implements and interface, but it does define the method as methods are defined within that interface.

Am I making sense?